This invention relates to sprayable hot melt adhesives based upon propylene copolymers and methods to apply these hot melt adhesives, particularly in disposables, packaging, labeling, bookbinding, woodworking and other assembly applications and articles produced by such methods.
Sprayable hot melt adhesives are desirable for the economic and commercial reasons that they can be thinly, evenly and quickly coated onto a substrate, saving in both time and material, and that they allow better substrate coverage per quantity of adhesive. Typical sprayable hot melt adhesives comprise an amorphous copolymer, generally a butene based copolymer or a styrene based block copolymer, combined with a tackifier.
For example, U.S. Pat. No. 4,959,207 discloses sprayable hot melt adhesives of butene copolymers having up to 5.5 to 10 weight % ethylene, tackifier and amorphous diluent having a softening point greater than 90xc2x0 C. Similarly, EP 442 045 A2 discloses sprayable hot melt adhesives of amorphous polyalphaolefins having 3 to 75 weight % C4 to C10 alpha-olefin, 25 to 95 weight % propylene 0 to 20 weight % ethylene.
JP-4180981 A addresses the problem of coagulation at the nozzle head by disclosing a hot melt adhesives of wax, bivalent phenol stabilizer, partially maleated or fumarated rosin ester tackifier and ethylene copolymer of ethylene mono-carboxylic vinyl ester/acrylic ester and suggesting that they will not clog the nozzle head when sprayed. However, when actually sprayed these hot melt adhesives will not produce a regular even pattern.
Similarly, WO 94 10256 discloses ethylene copolymer blends for hot melt adhesives. However these blends are not suggested for use in spraying applications.
The instant application relates to U.S. Ser. No. 60/171,715, filed Dec. 21, 1999.
Other references of interest include U.S. Pat. Nos. 6,156,856, 6,160,071, 4,642,269, 5,854,354, EP 0 622 380 B1, EP769 505 B1, EP 685 495 B1, U.S. Pat. Nos. 6,084,048, and 6,121,401.
Thus, this invention provides new sprayable hot melt adhesive compositions based upon propylene copolymers.
This invention relates a process for atomizing, spiral spraying, oscillation spraying or melt blowing copolymers onto a substrate comprising selecting a poly-alpha olefin inter-polymer comprising:
A) from 60 to 94% of units derived from one alpha mono-olefin having from 3 to 6 carbon atoms, and
B) from 6 to 40 mol % of units derived from ethylene one or more mono-olefins having from 4 to 10 carbon atoms and at least one carbon atom more than A); and
C) optionally from 0 to 10 mol % of units derived from another copolymerizable unsaturated hydrocarbon, different from A) and B);
wherein the copolymer has:
an Mw/Mn of 6 or less;
a storage modulus Gxe2x80x2 intersecting a value of 0.3 MPa at a temperature of less than 85xc2x0 C. when measured at a frequency of 1 Hz,
a Gxe2x80x3/Gxe2x80x2 ratio of 18 or more when Gxe2x80x2 is 10 Pa, and
a viscosity of 5000 mPaxc2x7sec or less at 190xc2x0 C., and
atomizing, spiral spraying, oscillation spraying or melt blowing the inter-polymer onto a substrate.
Blends of two or more different polymers having the above characteristics may also be used in this invention.